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How do I remove air bubble in oil-filled compass?

Discussion in 'General Scuba Equipment Discussions' started by EANx, Aug 27, 2018.

  1. EANx

    EANx Instructor, Scuba

    How annoying that all my underwater compasses get these growing gas bubbles after a while? :mad:

    -But how does one remove the bubble??
  2. Jack Hammer

    Jack Hammer Solo Diver

    I just buy a new compass at that point.
    giffenk likes this.
  3. EANx

    EANx Instructor, Scuba

  4. Jack Hammer

    Jack Hammer Solo Diver

    Every one I've had the bubble get big in began sticking and giving false readings. If you are handy enough you could drill a hole, top off with mineral oil, reseal, and be happy with your bubble free compass. I just buy a new one every 3 or 4 years.
    tridacna likes this.
  5. Wookie

    Wookie Secret Field Agent ScubaBoard Business Sponsor

  6. GJC

    GJC Solo Diver

    # of Dives: 200 - 499
    Location: Southern California, USA
    I tried fixing one once. Despite filling it and sealing, the next day there was a bigger bubble. Then I learned you have to have the fluid in a vacuum for a while before sealing to remove air that is dissolved in the fluid before you seal it. Not worth my time and effort. Bought a new compass.
  7. Akimbo

    Akimbo Lift to Freedom Volunteer Staff Member ScubaBoard Supporter

    I always used the bubble like a level since the diver is a substitute for a gimbal.
    Rooster59, Namreg 58, scrane and 2 others like this.
  8. Heruhur

    Heruhur Assistant Instructor

    # of Dives: 200 - 499
    Location: The Netherlands
    A bubble is usually an indicator that the compass has a leak.
    The bubble will only get bigger and after a while the compass will start to stick.
    A bubble in my compass is a replacement indicator for me . . . . .
    gizmo1972 and Colliam7 like this.
  9. broncobowsher

    broncobowsher Solo Diver

    same here. So easy to get a compass cocked enough to lock up. If the bubble is rolling around at the top, you are level enough for the compass to work.
  10. Just Anthony

    Just Anthony Angel Fish

    # of Dives: 100 - 199
    Location: Morehead City, NC ~ Wreck Divin Capitol of the USA
    A sealed compass is like a scuba tank you leave in your car in the summer. What's inside expands and contracts with the temperature.

    The bubble is there so the silica oil can expand in the heat without bursting the glass. That expanding silica oil has to have somewhere to go under pressure.

    Air is "squeezable", Liquid is not. Remember?

    So if you had a compass that was sealed and had no air in it, and say you left it lying on the dive boat seat in august in the noon sun, the liquid has room to expand without increasing the pressure very much inside the globe.

    Military-style dive compasses are built to withstand pressure changes. Most dive compasses just have cheap plastic cases. Plastic doesn't handle pressure changes very well.

    If the bubble grows to the point it's causing the needle to not function properly, then that's a leak. Otherwise an air bubble is normal.

    My boat compass has a dime-sized bubble in it. The temperature in my garage in February is a lot different than the temperature is when I'm beached at Radio Island in August. That bubble allows the oil in the compass to expand and contract without increasing the internal pressure very much. On most boat compasses, there's a little brass screw you can remove on the bottom and turn it upside down to add more liquid silicon to it. Wrist mounted scuba compasses don't have that feature. They're made cheap and intended to be replaced when they start leaking.
    ams511 likes this.

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